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Electron microscopy of seed-storage globulins.
Archives of Biochemistry and Biophysics
|September 1, 1985
Summary
Electron microscopy revealed diverse quaternary structures for seed globulins, including 7S disc-like proteins and 11S spherical proteins. These varied structures highlight evolutionary adaptations in plant seed storage proteins.
Area of Science:
- Biochemistry
- Structural Biology
- Plant Science
Background:
- Seed globulins are crucial storage proteins in plants, providing essential amino acids for germination.
- Understanding their quaternary structure is key to comprehending their function and evolution.
Purpose of the Study:
- To investigate and compare the quaternary structures of various seed globulins using electron microscopy.
- To elucidate the structural diversity among 7S and 11S globulins and related seed storage proteins.
Main Methods:
- Electron microscopy was employed to visualize the three-dimensional structures of purified seed globulins.
- Comparative analysis of images was performed to determine molecular dimensions and assembly patterns.
Main Results:
- Legume 7S globulins (phaseolin, beta-conglycinin, vicilin) presented as flat discs (ca. 8.5 nm diameter).
- Phaseolin exhibited a tetrameric 18S form at acidic pH, suggesting tetrahedral assembly.
- Classical 11S globulins (cucurbitin, legumin) appeared spherical (ca. 8.8 nm diameter).
- Lupin conglutin gamma (10S) showed a toroidal shape (ca. 10.3 nm outer diameter).
Conclusions:
- Seed globulin quaternary structures exhibit significant diversity, ranging from discs to spheres and toroids.
- These structural variations may reflect adaptations related to protein storage and mobilization within seeds.
- The quaternary structure of seed globulins is influenced by evolutionary constraints and functional requirements.